Fibrous cellulose esters, particularly cellulose acetate, are the commercially preferred media for filtration of smoke from filtered cigarettes. This commercial application consumes worldwide several hundred million pounds of cellulose acetate fiber per year. During the production of these filtered cigarettes, a certain percentage of them will not be brought to market, due to damage of goods, variation from specification, or other reasons. Those cigarette which are not sold are typically subjected to a reclamation process wherein the tobacco-laden portion of the cigarette is mechanically broken from the filter, and the tobacco is removed by shaking within a screening device. An example of this process is given in U.S. Pat. No. 3,224,451, which is incorporated herein by reference. After reclamation of tobacco, several tens of millions of pounds of residual material, referred to as "ripper waste" in the industry, comprised of cellulose acetate (typically plasticized for example with glycerol triacetate), paper, residual tobacco, and often flavors and fragrances remain; this ripper waste is most generally disposed of as landfill, representing both a loss of natural resources and a burden on landfill capacity.
The composition of ripper waste varies depending on the specifics of the cigarette products and the tobacco reclamation process employed. Typical composition ranges, by weight, of ripper waste are: a) cellulose acetate, 40-55%; b) plasticizer, 1-12%; c) paper, 25-45%; d) residual tobacco, 1-15%; e) adhesives, 2-3%; and f) flavors/fragrances, &lt;1%. Additional components, for example charcoal, may be found in these waste streams, depending on the specific cigarette product.
The physical/mechanical separations employed in reclaiming cigarette components have in the past either focused on sifting tobacco away from other components, as is the case in U.S. Pat. No. 3,224,451, or in the removal of cellulose acetate filter media from its paper liner, as in U.S. Pat. No. 4,261,790, which is incorporated herein by reference. Other approaches have included enzymatic degradation of the cellulose acetate to produce useful sugars, as in U.S. Pat. No. 4,298,013.
Isolation of cellulose acetate from ripper waste is insufficient to provide a recycled product of high commercial utility. During the manufacture of cigarettes, the cellulose acetate is treated with a plasticizer which improves the mechanical performance of the finished filter. The cellulose acetate may also be treated with flavorants, for example, menthol, and the cellulose acetate will absorb some levels of nicotine and other substances from the tobacco. If the cellulose acetate/plasticizer/flavors mixture is dissolved in a typical cellulose ester solvent, and reformed into a product, these extraneous substances will change both the mechanical and the sensory properties of the cellulose acetate, thereby reducing the overall quality of products manufactured with these recycled materials. Extraction with conventional solvents, such as ethanol, can be used to remove the majority of undesirable contaminants from cellulose acetate. But, the extraction solvents then become an undesirable contaminant, and reduces the product quality. An additional difficulty introduced by use of such extraction solvents is that they can escape into the environment, necessitating costly preventative measures.
The difficulties attendant in the use of conventional organic extractions can be avoided by use of a supercritical or near supercritical fluid extraction as in U.S. Pat. No. 5,328,934, which is incorporated herein by reference. In such a critical or near supercritical extraction process, a material which is gaseous under normal atmospheric temperatures and pressures, for example carbon dioxide, is converted into a high pressure solvent. This high pressure solvent can effectively dissolve the contaminants present in the filter tip waste, liberating these organic contaminants when the fluid's pressure and temperature are reduced. The extraction fluid used in this supercritical or near supercritical process can be effectively recycled within the process, and does not leave a residue within the recycled cellulose ester polymer product. While this high pressure process can effectively cleanse filter tip waste of it unwanted organic contaminants, it does require a significant capital investment for the construction of equipment vessels capable of safe operation under the relatively high pressures required to enter the supercritical or near supercritical region of most desirable fluids.
In U.S. Pat. No. 4,191,199, water is used to soften of glue seams in whole cigarettes. Once the tobacco column, that portion of the cigarette which actually contains the tobacco, has been opened, then free tobacco can be mechanically removed by traditional routes.
Water wash steps used in the manufacture of virgin cellulose ester polymer are well known to those skilled in the art. Such washing removes manufacturing residues such as long chain fatty acids, and acetic acid from the cellulose ester polymer. Such water washing of virgin cellulose ester polymers is described in U.S. Pat. Nos. 2,264,828, 2,860,132, and "Cellulose Acetate", Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Edition, John Wiley and Sons, New York.
Another application of water processing in the reclamation of cigarette waste is the reconstitution of small particles of tobacco, fines, recovered through traditional shaking/screening processes into a tobacco sheet or paper. An example of such a reconstitution process is given in U.S. Pat. No. 3,012,914.
The technical literature contains a great many references to the wet pulping of cellulose. Those familiar with the chemistry, binding properties, and solution properties of both cellulose acetate and cellulose will recognize that these two structural polymers share few common properties, and, therefore, must be treated as different materials. See, "Cellulose" and "Cellulose Acetate" Kirk-Othmer Encyclopedia of Chemical Technology, 3rd Edition, John Wiley and Sons, New York.